How to Test a Chainsaw Coil? – Using & Without a Multimeter

how to test a chainsaw coil

How to Test a Chainsaw Coil: A Comprehensive Guide

As an avid chainsaw user, keeping my equipment in top working order is essential for both performance and safety. A properly functioning chainsaw coil is critical to engine operation, yet this component can deteriorate over time. When the coil goes bad, the chainsaw may sputter, stall or fail to start altogether. Fortunately, testing a chainsaw coil is a straightforward process that can help diagnose issues before they become more serious. 

In this guide, I’ll provide a step-by-step overview of how to test both the primary and secondary circuits of a chainsaw coil using a multimeter. I’ll also discuss symptoms of a faulty coil, solutions for a Stihl chainsaw not oiling the bar, important safety precautions, and frequently asked questions. Equipped with this knowledge, you’ll be prepared to troubleshoot your chainsaw coil and get your saw running like new again. Let’s get started!

How to Test a Chainsaw Coil?

When a chainsaw engine is misfiring, bogging down under load, or having starting trouble, a bad coil is often the culprit. Testing the coil can confirm whether it needs to be replaced or if the issue lies elsewhere. Here’s an overview of the coil testing process:

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Symptoms of a Bad Chainsaw Coil

Watch for these common signs that your chainsaw coil may be faulty:

  • Difficulty starting or won’t start at all
  • Poor idle and stalling
  • Misfiring at high rpms
  • Loss of power and bogging down
  • Intermittent spark or no spark
  • Backfiring and popping sounds

If you notice any of these issues, it’s wise to test the coil before further use. A failing coil means ignition problems are on the horizon.

How to Test a Chainsaw Coil? - Using & Without a Multimeter

Locating the Spark Plug

The first step is accessing the spark plug that connects to the ignition coil. Consult your owner’s manual for model-specific location. On many chainsaws, the plug is found under a vented plastic cover. Use a screwdriver to remove the cover and access the plug.

Testing the Primary Circuit of the Coil

The primary circuit sends voltage from the magneto to the ignition coil. Use a multimeter to check resistance as follows:

  1. Disconnect the spark plug wire from the spark plug.
  2. Set the multimeter to Ohms setting, usually indicated by the omega symbol.
  3. Attach the multimeter leads to the spark plug wire tip and engine ground.
  4. Check the resistance reading – a good coil will show between 0.4 to 2 ohms.
  5. If the reading is infinity, there is a break in the circuit. If the reading is almost zero, there is a short. Either indicates a bad coil.

This simple check verifies whether the primary circuit is functioning properly before moving to the secondary circuit.

Testing the Secondary Circuit of the Coil

The secondary circuit transfers the boosted voltage from the coil to the spark plug. Use an insulated plug wire clip for this test:

  1. Reattach the spark plug wire to the spark plug.
  2. Set the multimeter to the Kilovolts setting, usually indicated by “kV” or “KV”.
  3. Attach the red probe from the multimeter to the insulated plug clip. Connect the clip securely over the metal end of the spark plug.
  4. Hold the black probe about 1/4 inch away from the metal tip on the spark plug.
  5. Pull the starter cord firmly to test for spark. A good coil will emit a blue snappy spark between the black probe and spark plug. An intermittent orange spark indicates a weak coil.
  6. Repeat the test several times. If there is no spark or weak spark each time, the coil is likely faulty.
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This method effectively diagnoses issues with the ignition coil’s secondary circuit so you can determine if a replacement coil is needed.

Frequently Asked Questions

How do I know if my chainsaw coil is bad?

Symptoms like difficulty starting, misfiring at high rpms, losing power, or intermittent spark indicate a possibly faulty coil. Testing with a multimeter is the best way to diagnose a problematic coil.

Can I test a chainsaw coil without a multimeter?

While a visual inspection may reveal external damage, testing the primary and secondary circuits requires a multimeter to get accurate resistance and voltage readings. Attempting to run the saw without properly testing the coil risks further engine damage.

How often should I test my chainsaw coil?

Regular maintenance is key for chainsaw upkeep. Test the coil each season before use and periodically check for symptoms of a failing coil. Proactive testing can catch issues before the saw quits working in the field.

What are the common causes of a chainsaw not oiling the bar?

An empty oil tank, clogged oil passages, leaking oil lines, faulty oiler pump, loose sprocket, or using the wrong bar oil can all prevent adequate lubrication. Following the proper diagnostic and repair steps addresses each potential issue.

How do I clean the oiler on my chainsaw?

Remove the clutch cover and bar to access the oil passages. Blow out any debris with compressed air and use a thin wire to clear channels. Flush with solvent spray cleaner. Reassemble and test oiler operation.

Can a bad chainsaw coil be repaired?

It’s usually not recommended to attempt coil repairs. The cost of a new coil is comparable to repair parts, and a faulty coil indicates winding issues within the sealed component. Install a manufacturer-approved replacement coil for optimal ignition function.

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How do I maintain my chainsaw for optimal performance?

Replace the spark plug and air filter yearly. Check the chain tension regularly and sharpen the chain as needed. Always use fresh fuel with the recommended oil mix. Clean the exterior, bar, and chain after each use. Follow the manufacturer’s maintenance schedule. Proper care maximizes saw life.


Troubleshooting issues with your chainsaw coil doesn’t need to be complicated – just follow the step-by-step testing methods I’ve outlined. Catching problems early prevents more extensive repairs down the road. Be diligent about chainsaw safety procedures too. With routine testing and maintenance, your saw will deliver years of smooth and reliable performance. Now you’re ready to diagnose coil issues, fix oiling problems, and keep your chainsaw running its best. Get out there and start cutting!

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